(1) Field of the Invention
The present invention relates to an antenna, especially relates to an antenna that is capable of switching directivity.
(2) Description of the Related Art
Conventionally, for example, users were adjusting a physical direction of an antenna in order to make a directivity of the antenna optimal for receiving television broadcasting signals by the antenna. However this adjusting method had a problem that this adjusting method was very difficult. So, for example, an antenna system having an indicator indicating a receiving condition of television broadcasting signals in order to manually adjust the physical direction of the antenna existed. Another antenna system that automatically adjusted the physical direction of the antenna upon user's request existed.
Further an antenna (so-called “smart antenna”) that can automatically change the direction of the antenna every time preferable channels are instructed by users is suggested.
FIG. 7 is a perspective view of the smart antenna 1. According to this figure, the smart antenna 1 is comprised of an antenna unit 2 with receiving element, a chassis 3 holding the antenna unit 2, shaft portion 4 supporting the chassis 3 at a predetermined height and fixing the chassis 3 to a television receiving device, and a wiring wired from the antenna unit 2 and electrically connected to the television receiving device. According to this configuration, the smart antenna 1 is controlled by the television receiving device based on a predetermined standard through the wiring and changes the directivity.
In case connecting the smart antenna 1 mentioned above to the television receiving device, the receiving element have to be placed at a height where is upper than the television receiving device in order to improve a sensitivity of the receiving element. For example, the sensitivity of the receiving element is improved by extending general indoor antennas as the receiving element for receiving the television broadcasting signals. However the smart antenna is horizontally placed in order to switch the directivity from horizontal directions. Therefore, the chassis 3 holding the antenna unit 2 has to be placed at a height where is upper than the television receiving device. Further the smart antenna 1 has to be placed at a position where is further from the television receiving device because the smart antenna 1 has high sensitivity.
In this case, problems mentioned below are occurred. That is, the smart antenna 1 can't avoid seeing because the smart antenna 1 is placed at the height where is upper than the television receiving device. Therefore, it is a problem that the smart antenna 1 defiles the television receiving device connected to the smart antenna 1.
Regarding general desktop antennas other than the smart antennas, for improvement in appearance, inventions mentioned below are disclosed. For example, technologies that chassis cover the antennas in order to camouflage the appearance of the antennas are disclosed in Japan published patent application publication No. H11-177466A, Japan published patent application publication No. 2001-85921A, Japan published utility application publication No. H05-6920U, Japan registered utility model patent No. 3041875U and Japan registered utility model patent No. 3044292U. According to these technologies, reducing user's sense of discomfort and making up for lack of aesthetic can be achieved.
A problem mentioned below occurs in case applying above mentioned inventions for the smart antennas. That is, it is not desired that conductive substances placed around the smart antennas because the smart antennas have the high sensitivities as mentioned above. Therefore the high sensitivities of the smart antennas are harmed by camouflaging the appearance of the smart antennas by the chassis.